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Discuss Height differential between soil pipe and loo's pipe in the Bathrooms, Showers and Wetrooms area at

  1. Greg

    Greg New Member

    The bottom edge of this soil pipe is 155mm from the new sub-floor. The bottom edge of this loo out-pipe is 130mm above the loo base. So there's a shortfall of -25mm. When I've added the levelling compound, Ditra uncoupling membrane, tile adhesive and tiles, I expect the loo to rise by between 16 & 23mm, so the disparity will then be -9mm to -2mm. Should the loo out-pipe be above the soil pipe or am I OK with these measurements?

  2. Greg

    Greg New Member

    Also, will a typical straight-through connector handle a minor case of shortism or should I plump for a flexi or offset connector?
  3. snowhead

    snowhead Well-Known Member

    The pan outlet at the worst needs to be level, ideally slightly higher to give a fall.

    What's the measurement of the bottom of the soil pipe at the wall.
    It looks like the pipe rises to the pan, you may be able to gain a bit if you cut it at the wall and use a long straight NON FLEXI connector.
  4. Greg

    Greg New Member

    I missed a bit, which is that there will be 250mm deep cabinet, concealing the cistern, so I'm going to have to change the soil pipe for one about 250mm longer, which will make the difference even more. I really don't want to adjust the soil pipe externally as I just replaced it and it'll be a pain (&££) to adjust it, having solvent welded a couple of bosses on for the sink and bath/shower. I guess if I have to, I have to. :(
  5. Greg

    Greg New Member

  6. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    I would try to aim about 5-10 mill higher (toilet spigot) than the soil pipe atm
  7. Ben-gee

    Ben-gee Active Member

    As you need to extend it, cut it back to the wall leaving enough for a socket (about 60mm). Join the correct length of rigid pipe that you need to this stub using a straight connector (either ring seal or solvent weld), when making this connection alter the angle slightly on each side of the socket to bring your new pipe down to the required height. These connections easily accommodate a 5 degree misalignment and that should get you where you need to be ie below your pan outlet.
  8. JCplumb

    JCplumb Plumber

    I have raised toilets in the past to solve this issue if it's been an inch or so.
    Use some plywood or similar hard wood to make a base with the same footprint as your toilet, sit the toilet on that, and do a nice silicone job with a fugi or similar after installation, you won't see it. If the base is too high for silicone alone, paint it white with some good exterior glossy paint.
    I did one about 2 inches thick and used white exterior gloss on the wood, you could see it if you looked for it but it looked fine.
  9. Best

    Best Trusted Plumber Top Contributor!!

    I would consider doing the cutting back method that others recommended, if pipe through wall is currently rising.
    But I see no problem at all with having to lower that junction through the wall. All you need is to cut the soil pipe below the socket that goes to the junction.
    Choice would be to either cut in the middle of the short plain piece of pipe and then cut the extra few mm you need to lower it all and then use a socket.
    Or cut the push fit socket below the junction off, remove extra you need and then fit a new socket - solvent to push fit type if you wanted.
    Got to cut the walls slightly though.
    p.s. - why did you put a clip on the smaller waste near where it goes into wall? Doesn’t need it there, better in the middle
  10. Greg

    Greg New Member

    Thanks for the advice, all. I'm going to take out the soil pipe shown in the image as I've got to use a longer pipe anyway, and see if it's just some masonry in the hole that's making it point up so much. If that doesn't allow me to a) match the hight of the pan pipe and b) have a bit of a slope down, then I'll adjust the stack to ensure a) & b) are achieved
    • Like Like x 1
  11. Greg

    Greg New Member

    Because I did the outside before I did the inside and needed something to push against when I solvent welded the inside pipe into that inspection joint, from the bathroom. Perhaps I should have solvent welded a stub of pipe from the the inspection joint through into the bathroom and then just used a straight coupler to join in to it. Done now though ;)
    • Like Like x 1
  12. Greg

    Greg New Member

    Coming back to my soil pipe issue. Is it OK to have around 500mm of horizontal soil pipe or does it have to have a slope toward the soil stack? If so how slopey should it be?
  13. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Around 15mm a meter you can go upto 25mm a meter but no more
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